Before we get on to cute young martens though, let’s first rewind back to last summer. Usually solitary animals, pine martens make an exception when duty calls and they pair up for breeding. These pairings are brief, with both males and females mating with several individuals through July and August.

With a gestation period of around 30 days, giving birth in autumn wouldn’t be wise with temperatures and prey availability dropping through the winter months. Instead, females employ a clever biological trick, delaying her pregnancy til sometime between January and March. This means the kits’ first few months will coincide with the warmer weather and plentiful prey that spring brings.

Between March and April, safe in a carefully selected cavity in a mature tree, the female gives birth to a small litter of silver-haired kits. Their eyes will not open until they are 5-weeks old, by which time their characteristic brown fur and creamy chest patch have grown through. The female marten rears the kits by herself (there are several potential fathers after all), tending to their every need; providing prey to chew on as they begin to wean, and even encouraging them to toilet with a tentative, albeit personal, lick around their rear.

As the kits grow, they become restless in their nest and start to explore, peaking out to the world beyond. At this point, it’s not uncommon for their mother to move them to a safer den site – a tree with rougher bark perhaps, so they can learn to climb without such a risk of falling. A young marten on the forest floor would be easy prey for a passing fox.

Once they become confident climbers, the young martens will accompany their mother on feeding trips, and will stick around in their mother’s territory for the next few months. By the following spring, they must disperse and establish territories of their own.

It will be another few years before these young martens breed for themselves, meaning they must survive until the age of two or three before they even think about starting the next generation. This slow reproduction, combined with small litter sizes which average just two or three kits, means that the pine marten’s ability to colonise new areas is limited and the natural expansion of the population is slow. That’s where active translocations like the project that saw them reintroduced to the Forest of Dean come in, giving the population a helping hand to recolonise parts of their former range.

You can find out more about Project Pine Marten in our short documentary below.